1. Field of the Invention
The present invention relates to a component material of vibration system part for a speaker device.
2. Description of Related Art
Conventionally, as a fabric material of a diaphragm being a vibration system part for a speaker device, there is normally used a woven fabric or a non-woven fabric of inorganic fiber such as carbon fiber, glass fiber and ceramic fiber and an organic fiber such as aramid fiber and a PBO fiber (polypara phenylene benzobis imidazole fiber).
In addition, the fabric material of the above-mentioned fiber is generally used in such a state that the fabric material is impregnated with a thermosetting resin and then hardened by hot press. Additionally, the above fabric material of the fiber is sometimes used in such a state that a material, such as paper, foam and thermoplastic resin, is laminated on the surface thereof.
The fabric material to which such process is applied is formed into a predetermined shape by hot press, and is mounted on an outer peripheral wall of a voice coil bobbin as a diaphragm.
There is known a joint sheet forming composition including a fiber-type rock wool made of basalt (e.g., see Japanese Patent Application Laid-open under No. 2000-104043).
In addition, there is known a thermoplastic synthetic resin injection molded product including a reinforcement material including a rock wool microfilaments having a fiber diameter of 1 to 10 μm and fiber length of 60 to 600 μm, produced by processing a material mixture mixed or combined with basalt by a predetermined method, and fibrous potassium titanate having a fiber diameter of 0.1 to 0.7 μm and a fiber length of 10 to 50 μm (see Japanese Patent Publication No. 1-32855). Further, there is known a fiber board for architecture produced by processing and forming, by a predetermined method, a fiber-type rock wool, made of basalt by a known producing method, having a length of substantially 1 to 50 mm and a fiber diameter of 1 to 20 μm, (see Japanese Patent Application Laid-open under No. 8-90721).
Though the carbon fiber is excellent in its light weight and high rigidity, it is expensive. Further, since the carbon fiber has conductive property, an insulation treatment is necessary for a current-carrying part.
Though the ceramic fiber is excellent in its high rigidity, it is problematically expensive. Further, it is problematic that the ceramic fiber is easily broken at the time of processing.
Though ultra-high strength fiber such as the aramid fiber and the PBO fiber is excellent in its light weight and high internal loss, it is problematically expensive. Further, the ultra-high strength fiber is difficult to cut at the time of processing, and since it has hygroscopic property, it is easily deformed in the high-temperature and high-humidity atmosphere. The above-mentioned fibers are expensive fibers generally called “highly functional fiber”.
A glass fiber being a general fiber is inexpensive, has no hygroscopic property and no conductive property, and has the high rigidity. Therefore, the glass fiber is used for an inexpensive diaphragm. However, since internal loss of the glass fiber is low, there is a problem to be solved in terms of sound quality.